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Steric Sea Level in CORE-Forced Simulations

Summary

We analyze sea level from a suite of global ocean-ice simulations using the interannualCORE atmospheric state to determine surface ocean boundary buoyancy and momentum fluxes. These CORE-II hindcast simulations are compared amongst themselves as well as to observational estimates for both global mean thermosteric sea level, linear trend patterns of thermosteric sea level and ocean heat content, and trends in dynamic sea level. The majority of the simulations agree with estimated global thermosteric sea level rise during the final 15 years of the simulations (1993-2007); however, the simulations are not consistent with observations during years 1948-1992. Regional sea level trends during 1993-2007 are broadly consistent with available satellite measures. In particular, the simulations reveal an increasing trend in dynamic sea level in the west Pacific and decreasing trend in the east, with this trend arising from wind shifts and regional changes in upper 700 m ocean heat content. The models also exhibit a rise in the subpolar North Atlantic associated with increased advection of warmer subtropical waters into the subpolar gyre. Sea level trends are predominantly associated with steric trends, with thermosteric effects generally far larger than halosteric effects except in the Arctic and North Atlantic. There is a dominance of anti-correlation between thermosteric and halosteric effects for much of the World Ocean, associated with density compensated changes in the ocean interior.